=(8+2x/25)(400-x)

=3200+32x-8x-2x？ /25

=-2x？ /25+24x+3200

2、4800=-2x？ /25+24x+3200

x？ -300x+20000=0

(x-200)(x- 100)=0

x=200 x= 100

According to the meaning of the question

x=200

3、y=-2x？ /25+24x+3200

=-2/25(x？ -300 times +22500)+5000

=-2/25(x- 150)？ +5000

∴x= 150 has a maximum value, and the maximum value is 5000.